The present invention relates to a metal thin film and a method of manufacturing the metal thin film, a dielectric capacitor and a method of manufacturing the dielectric capacitor, and a semiconductor device.
In recent years, accompanying advances in thin-film formation technology, a reduction in the size and an increase in the degree of integration of devices have been attempted by applying high-dielectric-constant characteristics of oxide dielectric thin-film materials to capacitors of semiconductor memories such as a DRAM. The degree of integration can be increased by applying ferroelectric characteristics to capacitors, and development of novel devices such as a ferroelectric memory (hereinafter indicated as “FeRAM”) which operates at high speed has progressed.
Since the FeRAM utilizes high-speed polarization reversal and remanent polarization of a ferroelectric thin film, the FeRAM has features such as high-speed write capability, nonvolatility, and low power consumption. Therefore, the FeRAM has attracted attention as the new next-generation memory. In the FeRAM, the remanent polarization direction of the ferroelectric capacitor is written by applying a voltage. Therefore, the FeRAM has an advantage in that the write speed is 1000 times or more and power consumption is 1/10 or less in comparison with an EEPROM in which data is written by injection of electrons by applying a high voltage to a tunnel oxide film.
The ferroelectric capacitor is generally formed by two electrode films and a ferroelectric film interposed between the electrode films. As the ferroelectric material, complex oxides such as a Pb-containing perovskite ferroelectric Pb(Zr,Ti)O3 (hereinafter may be called “PZT”) and a Bi-layer structured ferroelectric SrBi2Ta2O9 are well known. As the electrode film of the ferroelectric capacitor, noble metals such as Pt, Ir, and Ru or oxides of these metals are used due to their high thermal stability.
As the formation method for the ferroelectric film, a physical vapor deposition (PVD) method, a chemical vapor deposition (CVD) method, a solution coating method, and the like are generally utilized. As the formation method for the electrode film, a physical vapor deposition (PVD) method and a chemical vapor deposition (CVD) method are generally used.
In order to improve the performance and increase the degree of integration of the FeRAM, the ferroelectric capacitor is required to have a small size, low polarization-reversal voltage, large remanent polarization, small leakage current, and excellent fatigue resistance. In order to achieve this objective, various improvements have been made on the capacitor structure and the manufacturing method.
However, in spite of high material potential and long development history of the ferroelectric material, the FeRAM has been put on the market only as a product with a small degree of integration, that is, as a product with a large capacitor size. This is because characteristics such as the remanent polarization, leakage current, and fatigue resistance significantly deteriorate as the size of the ferroelectric capacitor is decreased.
As the reasons for deterioration of the capacitor characteristics accompanying a decrease in size, vaporization and diffusion of the capacitor material occurring during heat treatment, damage to the crystal occurring during capacitor etching, reduction of the ferroelectric film due to hydrogen produced during formation of an interlayer dielectric or a tungsten film, and the like can be given. In particular, deterioration of the capacitor characteristics due to hydrogen is a problem specific to the FeRAM manufacturing steps, and various techniques have been examined in order to solve this problem. These effects significantly decrease the remanent polarization of the capacitor from the initial value. Therefore, in order to realize a highly integrated FeRAM, development of process technology which prevents the effects of the process damage is indispensable.
In addition to preventing the process damage, it is effective to increase the remanent polarization of the capacitor in order to realize an increase in the degree of integration of the FeRAM. In order to increase the remanent polarization, it is necessary to sufficiently increase the crystallinity and the degree of crystal orientation of the ferroelectric film of the capacitor, for example.